Dynamic loss is significant for evaluating the performance of type-II high-temperature superconductor (HTS) coated conductors (CC), especially when used in electric machines. Although analytical expressions of dynamic loss have been proposed and verified for HTS CCs exposed to low external magnetic fields with a low current load rate, the non-linearity of dynamic loss at high current load ratios and simultaneous high magnetic fields is still unclear and cannot be predicted by the existing analytical equations. This paper proposes a completely new formulation to characterize the non-linearity of dynamic loss taking into account the J c(B) dependence of CCs, which can be used for full ranges of both magnetic fields and current load ratios. The proposed analytical formulas have been verified by a T -formulation based numerical model and experiments. This paper comprehensively demonstrates the variation of dynamic loss and provides a meaningful reference of loss controlling for HTS CCs, which is vital for HTS machine windings to avoid quench.

A superconductor has the unique properties of zero resistance and Meissner effect. Lenz's law is a fundamental law of physics. People have occasionally brought up the question that if a superconductor abides by Lenz's law. There has been lack of an explicit answer to this question so far. Recently, we carried out experiments with superconductor coils and a magnet in search of an answer to this question. We find out that the interacting behavior between a superconducting coil and a magnet does not comply with one of the primary interpretations of Lenz's law: the current induced in a circuit due to a change or a motion in a magnetic field is so directed as to exert a mechanical force opposing the motion. Our experimental results show that the induced current in the superconducting coil do not always oppose the motion of magnet during their interaction. Instead, in a certain portion of the interaction the induced current aids the motion of the magnet. This finding may require the aforementioned interpretation of Lenz's law to be revised as superconductors are involved.

High voltage direct current (HVDC) transmission technology has begun to play a great role in power transmission industry over the last decade. However, short-circuit fault seriously threatens the safety of an HVDC network. In order to reduce the fault current level of an HVDC network, utilizing a superconducting fault current limiter (SFCL) was proposed by researchers and engineers worldwide. Recently, Guangdong Grid Company of China Southern Power Grid, Co. has led a project to develop a 160 kV/1 kA resistive type DC SFCL. As a middle-step objective, a 160 kV/1 kA laboratory prototype has been developed. Due to a facility with an adequate capacity for testing such DC equipment is practically inaccessible, the current limiting performance of the prototype cannot be tested with a straightforward current limiting experiment. In practice, effectual alternative methods have to be adopted. Since the AC half-wave impact method requires less equipment and cost than the DC impact method, we took on an AC half wave impact current method to evaluate the current limiting function of the prototype alternatively. In this paper, we report the procedures and results of these tests.

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Lots of high-temperature superconducting (HTS) devices which require current leads, slip rings or brushes have to face the challenges such as large heat load and complex structure. Recently, an HTS energy converter has been proposed, which can not only induce but also exploit persistent current in a closed HTS ring, realizing the conversion of mechanical energy—electromagnetic energy—mechanical energy wirelessly. In this work, a dynamic modelling method based on the H-formulation and moving mesh has been proposed to accurately simulate the electromagnetic performance of the HTS energy converter. The proposed modelling method can depict the induced current density inside the superconductor and magnetic field distribution, serving as a powerful tool to analyze the complex working principle of the HTS energy converter. The validity of the model has been verified by experimental results. Besides, effects of different parameters of the energy converter have been investigated in detail by our proposed model, to provide further insight into the design and applications of the device.